Nitrogen management for wheat

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Chapter 11: 
Nitrogen Management for Wheat 
Production
In many fields, nitrogen (N) is the most limiting nutrient. The purpose of this chapter is to: 1) discuss the 
N cycle, 2) discuss how N fertilizer impacts wheat yields, 3) provide N fertilizer guidelines to maximize 
profitability, and 4) provide calculation examples.
Nitrogen cycle
Nitrogen (N) is present in various forms and passes from the atmosphere to the soil, living organisms, 
water, and then back into the atmosphere (Fig. 11.1). Industrial and atmospheric fixation processes 
can convert nitrogen gas (N₂) into inorganic N forms such as ammonium (NH₄+) and nitrate 
(NO₃-), which can be used by wheat. Some legume crops (e.g., alfalfa, clover, peas, and soybeans) in a 
symbiotic relationship with Rhizobia bacteria can also fix N2 into organic N, which is mineralized by 
microorganisms. 
 
Figure 11.1. A schematic diagram showing nitrogen cycling in agricultural soils. 
(Source: Sang Lee, SDSU)
Ron Gelderman
Sang Lee
BEST MANAGEMENT PRACTICES
WheatiGrow
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Soil or fertilizer inorganic N can be lost by leaching and denitrification before being utilized by wheat. For 
example, in some poorly drained soils, denitrification converts NO₃- to nitrous oxide (N₂O) or N₂, which 
is then lost to the atmosphere. Nitrous oxide (N₂O) is a concern because it is a greenhouse gas that traps 
approximately 298 times more heat than CO₂. Leaching of NO₃- to groundwater is most likely to occur in 
sandy soils and/or following large rainfalls. Volatilization losses of ammonia gas (NH₃) can occur when 
manure or urea [CO(NH₂)₂] is surface applied and not incorporated.
Nitrogen deficiency 
Wheat requires N to produce organic molecules like amino acids, proteins, and nucleic acids. Pale green 
plants are indicative of N deficiencies (Fig. 11.2). Other symptoms include chlorosis (yellowing), which 
commences on lower leaves beginning at the leaf tips and works inward, reduced tillering, stunting, poor 
kernel fill, and low grain protein. 
Nitrogen rates
Nitrogen fertilizer prices have increased in recent years, thus the application of N fertilizer in excess of the 
plant requirement can decrease producers’ potential profit and cause environmental problems. Whereas, 
applying too little N can reduce yields and wheat quality. Precision N management is necessary, therefore, 
to increase wheat production efficiency. Nitrogen rate recommendations for South Dakota wheat are based 
on yield goals, soil testing N levels, and cropping systems. The South Dakota State University (SDSU) 
current recommendation is 2.5 lbs of N per bushel, which is reduced by accounting for the various credits 
(Table 11.1). The amount of soil test nitrate-N (NO₃--N), manure N credit, and legume credits (if grown 
within the previous 2 years) are subtracted from the total N required for yield goals.
Figure 11.2. Nitrogen deficiency in wheat (N deficient 
rows on left with N sufficient rows on right). 
(Photo courtesy Jim Shroyer, KSU)
Table 11.1. Nitrogen recommendation for wheat in South Dakota. 
(Gerwing and Gelderman 2005)
N fertilizer recommendation (lbs N/acre) = (2.5 x RYG) - STN - LC - MNC
RYG = Realistic yield goal (bu/a)
STN = Soil test N value (lb N/a, 2 feet)
LC = Legume credit (lb N/a)
MNC = Manure N credit (lb N/a)
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Soil N credit
The residual N credit is the amount of NO₃--N contained in the surface 2 feet (24 inches). Since wheat is 
a short-season crop, N use by wheat is mainly from available soil N forms and depends less on organic 
N mineralization when compared to longer season crops such as corn or sunflowers. To determine an 
accurate soil N credit, the location and number of core samples are important. A general guideline for 
collecting soil samples is that between 15 to 20 cores should be composited from each uniform area 
that is sampled. To prevent mineralization (conversion of organic N to NH₄+ or NO₃-) and nitrification 
(conversion of NH₄+ to NO₃-), which will increase the soil test value, the field samples should be air dried 
or frozen within 12 hours of sampling. Additional information on methods of soil sampling is available in 
Gelderman et al. (2005).
Legume credits
The legume credit accounts for the amount of N that is mineralized from the previous crop. Legumes add 
N to the soil through symbiotic N fixation. Legume credits used in South Dakota are listed in Table 11.2. 
When seeding wheat into alfalfa and legume green manure crops using a no-tillage system, a half credit 
should be used in the current and following year (e.g., 50 lbs at 3-5 plants/sq ft) (Gerwing and Gelderman 
2005). 
Manure N credits
The amount of N available from manure depends on numerous factors including animal age, type of 
animal, storage characteristics, feed ratios, handling practices, and proposed application procedures. Due 
to these variations, the most accurate manure N credit is based on actual measured values. Additional 
background on collecting manure samples for nutrient analysis is available in NRCS (2002), Rieck-Hinz 
and Richard (2003), and Workman and Shapiro (2009). 
Manure analysis should include inorganic (ammonia) and organic N (Gerwing and Gelderman 2005). 
Credit 35% of the organic N in manure with first-year application, and credit 50% of the organic N if 
manure had been applied for 2 or more years. Credit 98% of the inorganic N if liquid manure is injected 
below the soil surface. If manure is broadcast on the surface and incorporated within 24 hours, credit 
90% of the inorganic N. When manure is not incorporated until 5 days after application, only 20% of the 
inorganic N should be used as a credit. If the manure is not sampled, N content estimation procedures are 
available in Gerwing and Gelderman (2005), Clay and Reitsma (2009) and Chapter 10.
Table 11.2. Legume nitrogen credits for nitrogen recommendations.
Previous crop Nitrogen credit (lb/a)
Soybeans, edible beans, peas, lentils 
and other annual legumes.
40
Alfalfa and legume green manure crop 
(sweet clover, red clover, etc.)
Plants/sq ft
5 and greater 150
3 - 5 100
1 - 2 50
1 or less 0
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Calculating the N recommendation
Once the yield goal and all credits (soil N credit, manure N credit, and legume credit) are determined, the 
N fertilizer recommendation can be calculated. An example calculation for N recommendation is shown 
in Table 11.3.
N materials, timing and placement 
An N fertilizer program must consider the N source, timing, rate, and placement (Fig. 11.3, Table 11.4). 
The two nitrogen materials most commonly used in South Dakota wheat production are dry urea (46-0-0) 
and liquid urea ammonium nitrate (UAN). The UAN can vary from 28 to 32% N and consists of ½ urea, ¼ 
ammonium and ¼ nitrate-N. The density of UAN (28-0-0) is approximately 10.6 lbs/gal, thus one gallon of 
28% UAN contains approximately 3 lbs of N.
The proper timing of N fertilizer is necessary for wheat production because the plants’ demand for N is 
tied to its growth stage (see Chapter 3 for more details on growth stages). Winter wheat requires relatively 
low N amounts in the fall, while N uptake increases rapidly when wheat starts growing rapidly (Feekes 
4-5) in the spring (Fig. 11.3). To meet this need, two N application options (a single application or a split 
application of N fertilizer) can be used. The first application can be made at planting, while the second 
should be applied prior to jointing or stem elongation (Feekes 4-5). It needs to be pointed out that N 
fertilizer should not be applied over snow.
Table 11.3. Sample N fertilizer calculations.
Wheat yield goal is 60 bu/a, 
Soil testing N (NO3-N in 2 feet depth) is 30 lb N/a, 
Previous crop was soybeans, 
Manure N credit (MNC) = 0,
N fertilizersource is urea with a fertilizer grade of (46-0-0),
Calculation for fertilizer required is:
 
€ 
N recommendation (lbs/acre) =
2.5 lbs N
bu
×
60 bushels
acre
−STN−LC −MNC
 STN =
30lbs
acre
; LC = 40 lbs
acre
; MNC = 0 lbs
acre
N recommendation = 150 lbs N
acre
−
30 lbs NO3
−
−N
acre
−
40 lbs
acre
−
0 lbs
acre
=
80 lbs N
acre
Urea (46% N) required =
80 lbs N
acre
×
lb urea
0.46 lbs N
=
174 lb urea
acre
 
 
Figure 11.3. Nitrogen uptake by winter wheat over the growing season. 
(Courtesy Murdock et al. UKY)
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For spring wheat, a similar approach can be followed, with a portion applied at planting and the remainder 
applied between V5 and jointing (Feekes 4-5) (Table 11.4). N applied too early can increase lodging and 
excessive tillering, while N applied too late can result in lower yields (Glover and Hall 2006; Ibrahim et al. 
2006; Otteson et al 2007). Late season N applications do not impact yield and may only increase protein. 
Generally, below ground N bands are more effective than surface applications. Nitrogen placement and 
timing options are provided in Table 11.5.
Table 11.4. Nitrogen timing influence on spring wheat yield near Brookings, SD.
Nitrogen Timing1 N rate Yield Yield Increase
lb/a ------ bu/a ------
Check 0 47 0
Planting 50 70 23
Tillering 50 70 23
Jointing 50 65 18
Boot 50 59 12
Heading 50 48 1
1 28 lb N/a, 2 feet nitrate soil test, broadcast ammonium nitrate.
Table 11.5. Nitrogen management options for winter and spring wheat.
Season Time of N application N placement options.
Fall Post-plant winter wheat Delay until soil temperature < 50 °F.
Avoid UAN, if leaching is possibility.
Subsurface applications are more efficient.
Winter Post-plant winter wheat Avoid on sloping, frozen soils.
Avoid application on snow-covered soils.
Early-mid spring Winter wheat-post Subsurface applications or incorporation are more efficient.
Spring wheat-preplant/plant Less volatilization losses when surface applied now (<60 °F temps) compared to 
later in spring. 
Late spring Post-plant UAN banded is preferred over urea if surface applied.
Consider urease inhibitor or poly-coated urea if surface applied.
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Summary
In-season N application on grain yields and grain quality are dependent on seasonal and site-specific 
environmental and wheat growth conditions. The time window for applying in-season N for wheat post-
plant is relatively short. If N is delayed until after tillering, the window can be only 1-2 weeks long. Relying 
on in-season N contains risk because: 1) wet conditions can prevent a timely application of the fertilizer, 
and 2) once the fertilizer is applied, rainfall is required to transport the N into the soil where it can be used 
by the plant.
The pre-plant N recommendations for spring wheat are dependent on many factors including soil 
texture, soil test N, labor and equipment needs, and variety (some varieties are very susceptible to 
lodging). If excellent growing conditions exist (good stands, tillering and soil moisture) before jointing 
and if it appears that actual yield could exceed yield goal, an in-season addition of 25 to 50 lbs of N can 
be considered. The market basis for high-protein wheat will also warrant consideration of in-season N 
applications. Application of N for winter wheat is usually made in the spring soon after greenup.
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Additional information and references
State Fertilizer recommendations Website
Nebraska Fertilizer recommendations http://cropwatch.unl.edu/web/wheat/soils
North Dakota Fertilizer recommendations http://www.ndsu.edu/fileadmin/soils/pdfs/sf882.pdf
Montana Micro-nutrients http://landresources.montana.edu/nm/Modules/Module7.pdf
Montana N recommendation http://landresources.montana.edu/nm/Modules/NM%203%20mt44493.pdf
Wyoming Recommendation http://uwadmnweb.uwyo.edu/soilfert/Pubs/Blaylock_etal_1996.pdf
Clay, D.E., and K.D. Reitsma. 2009. Soil fertility. In Clay, D.E., K.D. Reitsma, and S.A. Clay (eds). Best 
Management Practices for Corn Production in South Dakota. EC929. South Dakota State University, 
SDSU Extension, Brookings, SD. 
Gelderman R., J. Gerwing, and K. Reitsma. 2005. Recommended soil sampling methods for South 
Dakota. FS 935. College of Agriculture and Biological Sciences, South Dakota State University, SDSU 
Extension, South Dakota Department of Agriculture, Brookings. 
Gerwing, J., and R. Gelderman. 2005. Fertilizer recommendations guide. EC750. South Dakota State 
University, SDSU Extension, United States Department of Agriculture. Brookings, SD. 
Glover, K., and R.G. Hall. 2006. Traverse: A new high yielding and fusarium head blight tolerant spring 
wheat. B749. South Dakota State University, Agricultural Experiment Station, USDA. Available at 
http://www.sdwheat2.org/files/TraverseB749.pdf
Ibrahim, A., T. Nleya, and J. Rickertsen. 2006. Alice: A high yielding hard white winter wheat. B753. South 
Dakota State University, Agricultural Experiment Station, USDA. Available at http://www.sdwheat2.
org/files/Alice.pdf
Murdock, L., J. Grove, and G. Schwab. 1995. Fertilizer management. In Lee, C., and J. Herbek (eds). A 
Comprehensive Guide to Wheat Management in Kentucky. University of Kentucky, Cooperative 
Extension Service, Lexington, KY. Available at http://www.uky.edu/Ag/GrainCrops/ID125Section5.
html
NRCS. 2002. Sampling manure for nutrient management. SD-NRCS-FS-36. Available at ftp://ftp-fc.sc.egov.
usda.gov/SD/www/News/FactSheets/sampling.pdf
Otteson, B.N., M. Mergoum, and J.K. Ransom. 2007. Seeding rate and nitrogen management effects on 
spring wheat yield and yield components. Agron. J. 99:1615-1621.
Rieck-Hinz, A., and T.L. Richard. 2003. How to sample manure for nutrient analysis. PM 1558. Iowa State 
University Extension. Available at http://www.extension.iastate.edu/Publications/PM1558.pdf
Workmann, C.S., and C.A. Shapiro. 2009. Sampling manures for nutrient analysis. G1450. University of 
Nebraska–Lincoln Extension, Institute of Agriculture and Natural Resources, Lincoln, NE. Available at 
http://elkhorn.unl.edu/epublic/live/g1450/build/g1450.pdf
Acknowledgements
Support for this chapter was provided by South Dakota State University, South Dakota Wheat 
Commission, and South Dakota Soybean Research and Promotion Council.
Gelderman, R., and S. Lee. 2012. Nitrogen management for wheat production. In Clay, D.E., C.G. Carlson, 
and K. Dalsted (eds). iGrow Wheat: Best Management Practices for Wheat Production. South Dakota State 
University, SDSU Extension, Brookings, SD. 
http://cropwatch.unl.edu/web/wheat/soils
http://www.ndsu.edu/fileadmin/soils/pdfs/sf882.pdf
http://landresources.montana.edu/nm/Modules/Module7.pdf
http://landresources.montana.edu/nm/Modules/NM%203%20mt44493.pdf
http://uwadmnweb.uwyo.edu/soilfert/Pubs/Blaylock_etal_1996.pdf
http://www.sdwheat2.org/files/TraverseB749.pdf
http://www.sdwheat2.org/files/Alice.pdf
http://www.sdwheat2.org/files/Alice.pdf
http://www.uky.edu/Ag/GrainCrops/ID125Section5.html
http://www.uky.edu/Ag/GrainCrops/ID125Section5.html
ftp://ftp-fc.sc.egov.usda.gov/SD/www/News/FactSheets/sampling.pdf
ftp://ftp-fc.sc.egov.usda.gov/SD/www/News/FactSheets/sampling.pdf
http://www.extension.iastate.edu/Publications/PM1558.pdf
http://elkhorn.unl.edu/epublic/live/g1450/build/g1450.pdf
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